Molecular dynamics studies of the interactions of low energy particles and clusters with surfaces
Ghaly, Mai Abed El-Hamid
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https://hdl.handle.net/2142/20575
Description
Title
Molecular dynamics studies of the interactions of low energy particles and clusters with surfaces
Author(s)
Ghaly, Mai Abed El-Hamid
Issue Date
1995
Doctoral Committee Chair(s)
Averback, Robert S.
Department of Study
Nuclear, Plasma, and Radiological Engineering
Discipline
Nuclear Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Nuclear
Language
eng
Abstract
"The interaction of energetic particles and clusters with metal surfaces has been investigated using molecular dynamics computer simulations. For the particle interactions, a previously unknown mechanism for producing damage at surfaces, involving viscous flow of molten matter, was uncovered in atomistic simulations of self bombardment of Au, Cu and Pt. The findings were extended to higher energy irradiations using a macroscopic model derived in this work and shown to have enormous significance for studies of radiation damage and ion beam modifications of materials. The simulations also provide new insight into the question of ""non-linear"" or thermal spike sputtering and also suggest a mechanism for cluster emission. Cluster-solid interactions were investigated by simulating the impact of various metallic clusters on metal surfaces. The energies of the clusters were varied from less than one eV (soft landings) to over 3 keV; the sizes of the clusters were varied from 87 to 1000 atom, and the angles of incidence was varied from near glancing to near normal. Both solid and liquid clusters were examined. A broad range of behavior was observed in the simulations: splatting of the cluster over the surface, the formation of globs, and the penetration of the clusters deep into the substrate. General rules for predicting the dominant behavior are suggested."
Embedded atom method potentials were employed in these simulations to represent the different metals and alloys. Although these potentials are well tested near equilibrium conditions, they are unreliable when the potential energies exceeded $\approx$ 10 eV. Pseudopotential methods were employed to construct an accurate force model for atoms at the close separations, although a simple spline connecting EAM potentials at low energies with the Universal potential at high energies was employed in most of the simulations. All of the simulations were three dimensional and fully dynamical.
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